Just out of interest chap, is the 28mm one the same shape as the normal ones. I wondered if it might be totally different on a P100 ( don't they have leaf springs? ). Any chance of a pic?

I have worked my way from a 2wd Saph rear arb, to a 4x4 one and then the Escos one.
It is a lot stiffer ( 3.5 times I think ) but am just running with normal clamp bushes rather than Powerflex at the moment ( although I can option to those to introduce a bit more stiffness out of the package at any time ). I got it as Mike R ran one on his old Moonstone Blue Sapphire and that handled really well when I went in it at Donington. I also partly got it in anticipation of the 'tighter' VC diff which tends to introduce more initial corner entry 'push.
I've stuck with 2wd Sapph hubs at the moment as I'm running std ride at the front and also most of the roads round here are quite bumpy so I'd prefer the extra stability of the Sapphire hubs rather than trade-off for the enhanced turn-in ( but increased nervousness ) of the earlier 3-door type.